Normally standard aerial CATV amplifiers are utilized for underground system applications. Because these amplifiers are intended for aerial use, their input and output connectors are on opposite ends of the amplifier and are therefore not well suited for underground applications where all cables, both input and output, come from the same direction. To alleviate this problem especially for underground mounted configurations, special 180.degree. connectors are used on the output side of the amplifier. Thus all input and output terminals are made to face in the same direction. However, these connectors are both expensive and difficult to install.
Using aerial amplifers underground also presents a space problem since no attempt is made to keep them relatively small. As a result, large enclosures are needed which are expensive and more difficult to install, thereby increasing installation costs. Moreover, for under the surface mounting, there is at present no way to waterproof the aerial housing configuration adequately and when the vault floods, the amplifier is covered with water. The amplifier itself is waterpoof so that no water usually enters the housing, but the case itself is usually made of aluminum which corrodes easily.